Time domain localized-density-matrix method

A recently developed linear scaling localized-density-matrix method is modified, and the equation of motion for reduced single electron density matrix is solved for the absorption spectra of polyacetylene oligomers in the time-domain. The modified method requires much less computer memory which enables us to calculate linear optical response of larger oligomers containing up to 2000 carbon atoms. Different values of critical lengths are employed in the calculations, and their roles are clarified.